Stoichiometry-, phase- and orientation-controlled growth of polycrystalline pyrite (FeS 2) thin films by MOCVD

Abstract

The growth process of polycrystalline pyrite thin films employing low pressure metalorganic chemical vapor deposition (LP-MOCVD) in a vertical cold wall reactor has been investigated. Iron pentacarbonyl (IPC) and t-butyldisulfide (TBDS) were utilized as precursors. Study of the growth rate as a function of temperature reveals a kinetically controlled growth process with an activation energy of 73 kJ / mol over the temperature range from 250 to 400°C. From 500 to 630°C, the growth rate is mainly mass transport limited. Decomposition of the films into pyrrhotite (Fe 1 − x S) occurs at higher growth temperatures. The S Fe ratio in the films has been controlled from 1.23 up to 2.03 by changing the TBDS partial pressure. With increasing deposition temperature, the crystallites in the films show the tendency to grow [100]-oriented on amorphous substrates at a growth rate of 2.5 Å / s. The grains show a preferential orientation in the [111] direction upon lowering the growth rate down to 0.3 Å / s. Temperatures above 550°C are beneficial in enhancing the grain size in the columnar structured films up to 1.0 μm.